Know your stone
These are the stones we actually work with. For each one: the mineral family it belongs to, its hardness on the Mohs scale, the colours it typically shows, and the reason it looks the way it does.
We describe material and appearance only. Nothing here claims a stone affects health, mood or fortune.
Feldspar group (orthoclase)
Moonstone's floating sheen - adularescence - comes from its internal structure rather than its colour: the stone is built from alternating microscopic layers of two feldspars, and light scattering between those layers throws back a soft blue-white glow.
Quartz (macrocrystalline)
Amethyst is ordinary quartz whose violet colour comes from traces of iron in the crystal structure, altered by natural irradiation. The colour grows in bands as the crystal forms, which is why one end of a cut bead is often stronger than the other.
Quartz (macrocrystalline)
Rose quartz owes its pink to microscopic fibrous inclusions of a borosilicate mineral distributed through the quartz, not to a dissolved colouring agent. Those inclusions also scatter light, which is why the stone reads as translucent and milky rather than glassy-clear.
Quartz (macrocrystalline)
Clear quartz is silicon dioxide grown in a repeating three-dimensional lattice, and it grows as six-sided prisms because of that lattice. Its internal wisps are healed fractures and trapped fluid from the time the crystal formed.
Chalcedony (microcrystalline quartz)
Agate's banding is a record of deposition: silica-rich fluid entered a cavity in volcanic rock and laid down layer after layer of fine-grained chalcedony against the cavity wall, each layer differing slightly in trace content and grain size. No two slices repeat.
Two distinct minerals share the name: nephrite (amphibole group) and jadeite (pyroxene group)
Both jades are interlocking-fibre aggregates rather than single crystals, and that felted internal structure is why jade resists chipping and can be carved thin - toughness, which measures resistance to breaking, is not the same property as hardness, which measures resistance to scratching.
Feldspar group (plagioclase)
That flash - labradorescence - is interference, not pigment. The stone separated as it cooled into extremely thin alternating lamellae of two feldspar compositions, and light reflecting off those internal layers interferes with itself, returning one narrow band of colour at one particular viewing angle.
Chalcedony (microcrystalline quartz)
Onyx is banded chalcedony - the same layered silica structure as agate, but with the bands lying in flat parallel planes rather than concentric rings. Uniformly black material is uncommon in nature, so most black onyx on the market is pale chalcedony darkened by a long-established sugar-and-acid treatment that deposits carbon in its pores.
Quartz (macrocrystalline) with platy mineral inclusions
The glitter, called aventurescence, comes from inclusions rather than the quartz itself: thousands of tiny flat plates of mica lie scattered through the stone, and each one reflects light like a small mirror. The green body colour comes from a chromium-bearing mica variety.
Quartz (fibrous, formed by replacement of crocidolite)
Tiger's eye began as crocidolite, a fibrous blue mineral, whose fibres were replaced by quartz while their parallel alignment survived. Light reflecting off that fibre bundle concentrates into a single moving band - chatoyancy - which always runs at right angles to the fibres, so the cutter's orientation decides where it falls.
